Lecture 18 Hemolytic Anemias Immune Anemias
Secondary WAIHA is associated with what? (5)
1. lymphoproliferative diseases (chronic lymphocytic leukemia, hodgkins disease) 2. neoplastic diseases 3. autoimmune disorders (lupus, rhumetoid arthritus, crohns disease) 4. viral and bacterial infections 5. vaccines
What is the basic path of IgG mediated? (5 steps)
1.first IgG attaches to the RBC membrane by the Fab region 2.The Fc receptor on the macrophages of the spleen binds to the Ab attached to the RBC 3.The macrophage pits the Ag/Ab complex and damages the cell 4.The RBC reseals its self and this process continues until the RBC forms a spherocyte 5.Then it is phagocytized by splenic macrophages
Cold AIHA accounts for what percentage of AIHA?
16-30%
What % does Paroxysmal Cold Hemoglobinuria (PCH) account for in all AIHA children?
30-40%
At what temp to warm AHIA have optimal reactivity?
37 degrees C
What temp does cold AIHA reach optimal reactivity?
<37 degrees C
What happens to the Donath landsteiner antibody at temps <20 and 37C?
At <20C the antibody binds to RBC and activates complement At 37C the antibody detaches from the cell but the MAC components are activated and lyse the cells
What marker is used for sensitized RBC?
C3b
What causes Paroxysmal Cold Hemoglobinuria (PCH)?
Donath landsteiner antibody - bi-phasic complement fixing IgG antibody
What are two scenarios when alloimmune HA may occur?
HDFN - mother makes antibodies against the antigens on the fetal RBC or transfusions
In Paroxysmal Cold Hemoglobinuria (PCH), what happen during the attack? (chemical levels) (13)
Hb drops sharply and is accompanied by hemoglobinemia, methanalbuminemia, hemoglobinuria neutropenia reticulocytopenia spherocytes increased bilirubin, BUN, LD decreased serum complement and haptoglobin
What antibody is warm AHIA medicated by usually?
IgG (IgG1 or IgG3)
What 3 mechanism types are there for hemolysis?
IgG mediated complement mediated IgM mediated
Cold AIHA is associated with which antibody usually?
IgM (rarely IgA or IgG)
In the initiation of the classic pathway, what antibody classes can be involved? (4)
IgM, IgG1, and IgG3 (sometimes IgG2)
What antigen is PCH antibody specific?
P-antigen (autoanti-P)
Is erythrophagocytosis more common in PCH or AHIA?
PCH
in Cold AIHA, How do you differentiate between benign cold agglutinins and pathologic cold agglutinins?
Pathogenic +DAT for poly specific AHG and monospecific agglutinates RBCs at 0-20C in saline titer usually >1:1000 (normal 1:64) Benign +DAT for poly specific AHG and monospecific anticomplement antiserum agglutinates RBCs at 0-4C titer usually up 1:64
What are the 2 types of WAIHA?
Primary: acute idiopathic WAIHA chronic idiopathic WAIHA
What does direct antiglobulin test (DAT) detect? and when is it used?
RBCs coated in vivo differentiates AIHA from other types of hemolytic anemias
What do most antibodies react with in warm AHIA?
Rh protein complex and occasionally have single specificity within Rh system (anti-e)
True/ False Hemoglobinuria and splenomegaly are clinical findings in Cold AIHA
True
If spherocytes are present how would you differentiate WAIHA from hereditary spherocytosis? (3 ways)
WAIHA +DAT / HS -DAT autohemolysis test WAIHA not corrected by glucose / HS is corrected by glucose PB WAIHA non-homogenous pop of spherocytes / HS homogenous pop
What 3 sub categories does autoimmune hemolytic anemia (AIHA) have?
Warm antibody autoimmune HA (WAIHA) Cold antibody AIHA (cold agglutinin disease) Mixed type AIHA (both warm and cold antibodies)
What initiated the classic pathway?
a antigen-antibody reaction
What two techniques can be used to detect and identify the causative antibody of the IHA?
agglutination in saline which detects IgM antibodies antihuman globulin (AHG) which detects IgG antibodies and or complement
In cold AHIA, polyclonal autoantibodies have a specificity for antigens in the Ii-system. What is associated with each of these? anti-I and anti-Pr
anti-I M - pneumoniae or infectious monomucleosis anti-Pr - varicella, rubella
What is drug independent in drug induced HA?
antibodies that react in vitro without the presence of the drug uses intravascular hemolysis
What is alloimmune hemolytic anemia?
antibody development to RBC antigen an individual lacks. EX: if someone receives a transfusion with foreign antigens the body may stimulate production of antibodies to destroy those cells but not harm the individuals own cells
What are the 3 categories of immune hemolytic anemias that are based on the stimulus of antibody production?
autoimmune hemolytic anemia drug-induced hemolytic anemia alloiummune hemolytic anemia
How is alloimmune HA detected?
by antibody screen test (indirect AHg test)
How is mixed-type AIHA characterized?
by the presence of a warm reacting IgG autoantibody and cold reacting IgM autoantibody that both have high titer and high thermal amplitude
In some cases Cold AIHA is associated with what types of anemias? (2)
chronic and episodic hemolytic anemia
The complement cascade can be initiated by what 3 mechanisms?
classic, alternative, and lectin mechanism
Is splenomegaly common or uncommon in WAIHA?
common
What therapy is used for Mixed-type AIHA?
corticosteroids without transfusions
What laboratory findings might there be to suggest anemia?
decreased HGB, HCT, and haptoglobin increased retics and/or uconjugated bilirubin
What two types of antihuman globulin (AHG) tests that can be preformed?
direct antiglobulin test (DAT) indirect antoglobulin test (IAT)
What are the classical mechanisms for Drug-induced hemolytic anemia? (4)
drug absorption immune complex formation autoantibody induction membrane modification
What are the two types of drug induced antibodies?
drug dependent drug independent
What are the two sub categories of drug induced HA? How are they classified?
drug-independent drug-dependent Based on the reaction of the patients RBCs and drug in the vitro test system
What are new DAT techniques that are more sensitive? (4)
enzyme linked DAT gel test flow cytometry polybrene test
What laboratory findings might there be in the BM for WAIHA?
erythroid hyperplasia and erythrophagocytosis
Which hemolysis is most common? intra or exra
extravascular
What mechanism of hemolysis does warm AHIA use?
extravascular via splenic macrophages
What does Cold AIHA do to automated blood counts?
falsely decreased RBCs falsely increases MCV
What are three factors that can cause autoimmune disease?
genetic predisposition exposure to infectious agents defects in regulation of immune tolerance
What clinical symptoms can be found in those with Paroxysmal Cold Hemoglobinuria (PCH)? (5)
hemoglobinuria (most common) jaundice, pallor, heptatosplenomegaly, Raynaud's phenomenon can occur
When does extravascular hemolysis occur?
if the RBC has been sensitized with the Ab or complement then it is removed from circulation buy the spleen or liver and phagocytized by macrophages
When does intravascular hemolysis occur?
if the complement cascade is activated by C9 (membrane attack complex) resulting in lysis
What are the difference between immediate and delayed reactions in hemolytic transfusions?
immediate IgM and occur within 24hrs of transfusion, intravascular hemolysis delayed IgG and occur 2-14 days after transfusion, extravascular hemolysis
Hemolytic transfusion reactions have two different types of reactions what are they?
immediate and delayed
What normally prevents the formation of autoantobodies?
immune tolerance which is when your body recognizes self antigens but does not destroy them
What is the first line of therapy for patients with WAIHA?
immunosuppressive drugs such as corticosteroids
When is a positive DAT seen?
in normal individuals
What is secondary CAS (cold agglutinated anemia)? (2)
infectious disease and lymphoproliferative disorders
What can cause a negative DAT in AIHA? (3)
insufficient number of IgG molecules on RBC autoantibodies of IgA or IgM classq Autoantibodies with low affinity for RBC
What conditions must be require for intravascular hemolysis or extravascular hemolysis to occur in IgM mediated hemolysis?
intra - the complement activation is done through C9 extra - activation is incomplete and Cb3 coats the RBC and adheres to CR1 and CR3 receptors on macrophages
What hemolysis is most common in cold AIHA?
intravascular
Not only can IgM activate complements, what else can it do?
it can agglutinate cells
What changes does CAS do to vascular components? (2)
it causes vascular changes like: acrocyanosis (hands and/or feet turn blue and cold) raynaud's phenomenon (pain with pattern changes in the skin from white to blue to red)
What is immune hemolytic anemia?
it is a disorder where RBCs are destroyed prematurely by the immune process that is mediated by antibodies and or complements
What is Paroxysmal Cold Hemoglobinuria (PCH)?
it is a rare autoimmune hemolytic disorder that can occur at any age and characterized by massive intermittent acute hemolysis and hemoglobinuria
What is drug dependent in drug induced HA?
it requires the presence of drug during testing and uses uses extra and intravascular hemolysis
What therapy is there for Cold AIHA? (3)
keep extremities warm Chemotherapy for secondary to lymphoproliferative disorder plasma exchange for acute hemolytic episodes (produces more IgM)
50% of Mixed-type AIHA cases are idiopathic, what is the other half associated with?
lymphoproliferative diseases, autoimmune diseases, or HIV
In IgG mediated hemolysis what cells can phagocytize the RBCs? (2)
macrophages and neutrophils
Why are RBCs with IgM attached removed from circulation in a different manner than IgG?
macrophages do not have the receptors for the Fc portion of IgM
Idiopathic WAIHA accounts for how many cases of warm AIHA?
meaning you dont know the cause 60%
What are common laboratory findings of WAIHA? (5)
mod to severe normocytic normochromic anemia + DAT prescense of autoantibody in the serum increased retics decreased haptoglobin
What results do you expect in Paroxysmal Cold Hemoglobinuria (PCH) for a DAT and IAT?
neg DAT for antibodies weak + DAT for complement +IAT if cold
What would you see in the BM of Cold AIHA? (1)
normoblastic hyperplasia
What would you see on the PB of Cold AIHA? (6)
normocytic normochromic polychromasia, spherocytes, clumps of RBC, nRBC, erythrophagocytosis
What age does WAIHA usually occur and what are the symptoms?
occur at any age but increased after 40 symptoms of anemia (fatigue, pallor...)
In Cold AIHA, where can RBC agglutination occur and what does it cause?
occurs in areas of the body that cool to the antibody thermal range and causes sludging of the blood to flow within the capillaries
What is the knew "unified" hypothesis for drug-induced HA?
once RBC binds to the RBc membrane, antibodies can be produced to react with epitopes specific to the drugs, with combination of drug and RBC protein, or with epitopes primarily found on the RBC membrane
Why is IgM more likely to activate the complement over IgG?
only one IgM is required while 2 IgGs are needed therefore IgM is more likely to occur
warm and cold AIHA can be further broken down into what two categories?
primary AIHA meaning there is no underlying disease or secondary AIHA meaning there is an underlying disease
What is the basis of autoimmune hemolytic anemia (AIHA)?
process characterized by an immune reaction against self antigens and shorten RBC survival
What reactions can antibodies have towards RBCS? (3)
sensitization (attachment of antibody to RBC), agglutination, or hemolysis
What 2 major roles does complement carry out in immune hemolytic anemia?
sensitization and lysis of RBCs
What are common laboratory findings in the PB of WAIHA? (4)
spherocytes, polychromasia, nRBCs, schistocytes
Other than immunosuppressive drugs, What other therapy options are there for WAIHA patients? (4)
splenectomy in severe cases Rituximab - monoclonal anti-CD20 (found on b-lymphs) IVIG - high does intravenous immuglobulin plasma exchange and plasmapheresis
Hemolysis can be intravascular or extravascular depending on what? (2)
the class of antibody and if the complement cascade can be full activated
Which complement activation pathway is the most important?
the classic pathway
Although the spleen is more efficient what other organ can remove heavily sensitized cells?
the liver
What is responsible for lytic attack on RBCs?
the membrane attack complex
Why is transfusion difficult as a therapy for WAIHA?
the patients autoantibodies usually react with the donors cells so its difficult to find a compatible donor
When is indirect antoglobulin test used? And what does it indicate?
to detect antibodies in plasma or serum indicates alloummunization of free autoantibodies in the patients serum
What therapies are there for Paroxysmal Cold Hemoglobinuria (PCH)? (4)
transfusion if hemolysis is severe plasmapheresis if hemolysis persists Rituximab avoid the cold
Where is alloimmune HA most commonly seen? (2)
transfusion reaction and hemolytic disease of the fetus and newborn (HDFN)
How severe is idiopathic cold AIHA? What age is it usually seen? What antibody is involved?
usually chronic occurs after age 50 involves monoclonal IgM/kappa with autoanti-I specificity
What infections is Paroxysmal Cold Hemoglobinuria (PCH) associated with?
viral and bacterial
Is warm or cold AHIA most common?
warm
AIHA can be sub categorized into what two groups?
warm and cold AIHA
What is drug-induced hemolytic anemia?
when a drug attaches to the RBC membrane or the drug alters it in some way
What is alloimmune HA?
when antibodies are produced to a RBC antigen that the individual lacks These antibodies only react with the cells that posses the antigen and not the individual's own RBC
When does sensitization occur in complement-mediated hemolysis?
when only a portion of the cascade is activated and deposited on the RBC membrane
In complement mediated hemolysis when does intravascular hemolysis occur?
when the C1-C9 complex activation is complete
When does lysis of RBCs occur in complement-mediated hemolysis?
when the entire complement system is activated and deposited on the RBC membrane
